Memory allocation for virtual machines using memory map

ABSTRACT

Apparatuses and methods associated with memory allocations for virtual machines are disclosed. In embodiments, an apparatus may include a processor; a plurality of memory modules; and a memory controller configured to provide a layout of the memory modules. The apparatus may further include a VMM configured to be operated by the processor to manage execution of a VM by the processor including selective allocation of the memory modules to the VM using the layout of the memory modules provided to the VMM by the memory controller. Other embodiments may be described and claimed.

TECHNICAL FIELD

Embodiments of the present disclosure are related to the field of dataprocessing, and in particular, memory avocations and error recovery forvirtual machines running on a host system.

BACKGROUND

There is a trend towards virtualization in the Enterprise and Officecomputing environments. In general, the ratios of virtual machines perhost have been steadily increasing. While currently it is not uncommonto have 10 virtual machines per host machine, it is estimated that thiswill increase to 15, 20, or more in the near future. Over the nextseveral years it is expected that the majority of computing environmentswill be virtualized. With host machines supporting more and more virtualmachines there is an increased concern with respect to availability ofvirtual machines on a host machine. The availability of virtual machineson a host machine can be impacted by any number of issues. One of theseissues is a memory module failure on the host machine.

Under the current architecture, typically, each virtual machine may bedistributed across a multitude of memory modules of the host machine,with the virtual machine taking up only a portion of each of thesememory modules. This type of allocation leads to an interleaved memoryallocation where each memory module may have a portion of a multitude ofvirtual machines residing on it. The benefit of this interleavedallocation is that it enables parallel access to the data of the virtualmachine because each memory module holding a portion of the virtualmachine can be accessed simultaneously. The interleaved architecture,however, has a draw back when it comes to virtual machine availability.Utilizing current architecture, whenever there is a memory modulefailure, all virtual machines on the host machine must be shut down, toenable the host machine to be restarted to exclude the failed memorymodule. Therefore, whenever a single memory module fails on a hostmachine it causes an outage of all virtual machines running on that hostmachine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a generalized virtual computing environment, according to someembodiments of the present disclosure.

FIG. 2 is a diagram of one possible configuration of host machine in thevirtual computing environment of FIG. 1, according to some embodimentsof the present disclosure.

FIG. 3 is a flow chart for the allocation of physical memory for virtualmachines according to some embodiments of the present disclosure.

FIG. 4 is a flow chart for the reallocation of a virtual machine in theevent of a memory module failure, according to some embodiments of thepresent disclosure.

FIG. 5 is a diagram depicting the error correction according to someembodiments of the present disclosure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof wherein like numeralsdesignate like parts throughout, and in which is shown, by way ofillustration, embodiments that may be practiced. IL is to be understoodthat other embodiments may be utilized and structural or logical changesmay be made without departing from the scope of the present disclosure.Therefore, the following detailed description is not to be taken in alimiting sense, and the scope of embodiments is defined by the appendedclaims and their equivalents.

Various operations may be described as multiple discrete actions oroperations in turn, in a manner that is most helpful in understandingthe claimed subject matter. However, the order of description should notbe construed as to imply that these operations are necessarily orderdependent. In particular, these operations may not be performed in theorder of presentation. Operations described may be performed in adifferent order than the described embodiment. Various additionaloperations may be performed and/or described operations may be omittedin additional embodiments.

For the purposes of the present disclosure, the phrase “A and/or B”means (A), (B), or (A and B). For the purposes of the presentdisclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B),(A and C), (B and C), or (A, B and C). The description may use thephrases “in an embodiment,” or “in embodiments,” which may each refer toone or more of the same or different embodiments. Furthermore, the terms“comprising,” “including,” “having,” and the like, as used with respectto embodiments of the present disclosure, are synonymous.

With reference to FIG. 1, there is illustrated a virtual computingenvironment 100 implemented on host machine 102, according to someembodiments of the present disclosure. In embodiments, virtual computingenvironment (hereinafter, simply virtual environment) 100 may beconfigured to simultaneously support multiple virtual machines,represented here as VM1-VM5. Host machine 102 in the virtual environment100 may be shared among the virtual machines, with a layer ofvirtualization software, such as virtual machine manager (VMM) 104,configured to coordinate usages of the resources of host machine 102 byvirtual machines VM1-VM5.

VMM 104 may be configured to provide an abstraction layer, which mayprovide an illusion of a complete system for running the virtualmachines. In other words, from the viewpoint of the virtual machine, VMM104 may be a virtualized set of hardware on which the virtual machineexecutes. Therefore, the combination of the underlying hardware of hostmachine 102 and the VMM 104 may provide an execution environment for thevirtual machines, VM1-VM5.

In embodiments, VMM 104 may be configured to receive requests for memoryresources from virtual machines, VM1-VM5. VMM 104 may also be adapted toreceive a memory module layout of the memory resources available on hostmachine 102, from host machine 102, e.g., a memory controller of hostmachine 102. VMM 104 may be further adapted to utilize the memory modulelayout to selectively allocate memory to satisfy the memory requestsfrom the virtual machines, VM1-VM5. In some embodiments, for each memoryrequest, VMM 104 may be adapted to determine a minimum number of memorymodules to satisfy the memory request and utilize this determination inselectively allocating the memory resource to the requesting VM. Thisselective allocation of memory will be described in further detailbelow.

In some embodiments, VMM 104 may execute directly on host machine 102,as depicted in FIG. 1. In other embodiments VMM 104 may execute within ahost operating system executing on host machine 102. VMM 104 may also bereferred to as virtualization software or hypervisor, which may beconsidered synonymous for purposes of this disclosure, unless thecontext clearly indicates otherwise; and thus, the terms may be usedinterchangeably.

Virtual machines may be separated into two types, a process virtualmachine and a system virtual machine. A process virtual machine isdesigned to run a single process or application while a system virtualmachine runs a guest operating system (OS) and guest applications.Virtual machines VM1-VM5 may be composed of process virtual machines,system virtual machines, or any combination thereof. For purposes ofillustration, five virtual machines, VM1-VM5, are depicted in FIG. 1;however, it will be apparent to one of ordinary skill in the art thatthe number of virtual machines is not a limiting factor and any numberof virtual machines could be included without departing from the scopeof the present disclosure.

In some embodiments, the guest OS of the virtual machines may be thesame, e.g. replicated virtual machines. In some embodiments, the guestOS may be the same as that of the underlying host OS. In otherembodiments, the OS of the virtual machines may differ between eachother and/or may differ from the execution environment of the underlyinghost machine 102.

Host machine 102 may also be referred to as a host platform or hosthardware, these terms may be considered synonymous for purposes of thisdisclosure, unless the context clearly indicates otherwise. Host machine102 is discussed further in the discussion of FIG. 2.

FIG. 2 illustrates a more detailed depiction of the hardware resourcesof host machine 102, from FIG. 1, for some embodiments of the presentdisclosure. Except for the teaching of the present disclosure, hostmachine 102 may be any one of a number of computing devices known in theart, portable or stationary, including, but not limited to, personalcomputers, workstations, servers, portable computers (ebooks,ultrabooks, laptops) and handheld devices such as a personal digitalassistants (PDA) or smartphones.

The host machine 102 hardware may be composed of memory 202, memorycontroller 206 and a processor 208. The processor may be coupled withthe memory controller 206 and the memory controller 206 may be coupledwith memory 202. It will be apparent to one of ordinary skill in the artthat the configuration of host machine 102 is not a limiting factor andthe hardware resource of host machine 102 may be configured in a varietyof ways without departing from the scope of this disclosure.Furthermore, additional components may be added without departing fromthe scope of this disclosure.

Memory 202 is composed of a plurality of memory modules, 204 a-j,collectively referred to as 204. Memory modules 204 may be any type ofmemory module, volatile or non-volatile, dynamic or static random accessmemory, flash, without departing from the scope of this disclosure. Forpurposes of illustration, memory 202, is depicted as being composed of10 memory modules, 204 a-j. One having ordinary skill in the art wouldrecognize that memory 202 could be composed of any number of memorymodules without departing from the scope of this disclosure.

Memory controller 206 may be configured to manage the flow of data toand from memory 202. Memory controller 206 may also be configured tocontain the logic necessary to read and write to memory 202. Inembodiments, memory controller 206 may be adapted to provide a memorymodule layout to VMM 104. The memory module layout provided by memorycontroller 206 may be in any form so long as it provides sufficientinformation for VMM 104 to utilize in allocating memory for the virtualmachines. For example, in some embodiments the memory module layoutcould be a listing of memory modules along with the beginning and endingaddress for each memory module. In other embodiments the memory modulelayout could be a listing of each memory address and the memory modulewhere each memory address resides. In still further embodiments thememory module layout may be divided by memory module with a listing ofeach address of the respective memory module. One of ordinary skill inthe art will recognize that there are a number of ways to present thisinformation to VMM 104 without departing from the scope of thisdisclosure.

Memory controller 206 may be further adapted to determine a memoryallocation for VMM 104. In some embodiments memory controller 206 may beadapted to determine a minimum number of memory modules to satisfy thememory requirements of VMM 104. In these embodiments, memory controller206 may be adapted to then select memory blocks such that VMM 104 wouldreside wholly within the minimum number of memory modules. In someinstances only a single memory module may be needed. In otherembodiments, memory controller 206 may be configured to make use of aportion of each available memory module. Memory controller 206 would dothis by selecting available memory blocks across all memory modules withavailable memory blocks. In still other embodiments, memory controller206 may be configured to make use of a portion of a number of memorymodules somewhere in between the minimum number of memory modules andthe total number of available memory modules. In some embodiments,memory controller 206 may be adapted to select memory blocks from memorymodules with sufficient availability to equally proportion VMM 104across the memory modules.

While memory controller 206 is depicted as being separate from processor208, one of ordinary skill in the art would appreciate that the memorycontroller could be integrated with the processor without departing fromthe scope of the disclosure. Further, without limitation, in generalprocessor 208 may be a single core or multi-core processors, available,e.g., from Intel Corporation of Santa Clara, Calif.

FIG. 3 is a process flow diagram 300 for allocating memory to thevirtual machines utilizing the VMM in accordance with some embodimentsof the present disclosure. This process will be described with referenceto elements of FIGS. 1 and 2 for clarity. The process may start at block302 in which VMM 104 may be activated. This may be done through the OSof the host system or through a hardware or firmware mechanism of hostmachine 102, depending upon the configuration of host machine 102. Atblock 304 the OS of the host system or the hardware or firmwaremechanism activating VMM 104 may allocate all or portions of one or morememory modules for VMM 104 in block 306. As discussed in reference toFIG. 2, in some embodiments the OS of the host system or the hardware orfirmware mechanism activating VMM 104 may be adapted to determine aminimum number of memory modules to satisfy the memory requirement forVMM 104.

After the memory modules for VMM 104 have been allocated and VMM 104 hasbeen fully instantiated, VMM 104 may submit a request to memorycontroller 206 for a memory module layout at block 308. As discussed inreference to FIG. 2 above, the memory controller 206 may be adapted toaccept and respond to such a request. In block 310 VMM 104 would receivethe memory module layout from memory controller 206. In alternateembodiments, memory controller 206 may be configured to automaticallyprovide the memory map to VMM 104, on initialization of VMM 104.

The memory module layout may be in any format so long as it iscompatible with VMM 104. For example, in some embodiments the memorymodule layout could be a listing of memory modules along with thebeginning and ending address for each memory module. In otherembodiments the memory module layout could be a listing of each memoryaddress and the memory module where that memory address resides. Instill further embodiments the memory module layout may be divided bymemory module with each address of the respective memory module listed.One of ordinary skill in the art will recognize that there is a numberof ways to present this information to VMM 104 without departing fromthe scope of this disclosure.

In block 312, after receipt of the memory map, VMM 104 may activate avirtual machine, such as VM1 of FIG. 1, in response to e.g., a VMrequest. VMM 104 may then determine the memory requirements for thevirtual machine being activated, or be provided with such information,e.g., by the virtual machine being activated, at block 314. In someembodiments memory requirements may be determined statically, based uponsome type of stored initialization settings for virtual machine VM1. Inother embodiments the memory requirements may be determined on the fly,or dynamically.

In block 316 VMM 104 may determine a selective memory allocation forvirtual machine VM1. VMM 104 may determine the selective memoryallocation by utilizing the memory module layout to select blocks ofmemory to satisfy the memory requirements of virtual machine VM1. VMM104 may select the memory blocks to allocate in a number of ways. Forexample, in some embodiments VMM 104 may be adapted to determine aminimum number of memory modules to satisfy the memory requirements ofvirtual machine VM1. In these embodiments, VMM 104 may then selectmemory blocks such that virtual machine VM1 would reside wholly withinthe minimum number of memory modules. In other embodiments, VMM 104 maymake use of a portion of each available memory module. VMM 104 would dothis by selecting available memory blocks across all memory modules withavailable memory blocks. In still other embodiments, VMM 104 may makeuse of a portion of a number of memory modules somewhere in between theminimum number and the total number of available memory modules. In someembodiments, VMM 104 may be adapted to select memory blocks from memorymodules with sufficient availability to equally proportion virtualmachine VM1 across the memory modules.

In some embodiments VMM 104 may record the details of the selectivememory allocation for later reference. These details may include theaddress ranges, or memory modules allocated to the virtual machine alongwith an identification of the virtual machine to which these addressesor memory modules have been allocated.

In block 320, a determination is made as to whether or not there aremore virtual machines to be activated. If there are more virtualmachines to be activated then the process described above may berepeated for each additional virtual machine to be activated, i.e. FIG.1 VM2-VM5. If all virtual machines have been activated this process mayend or be suspended until another virtual machine is to be activated.

FIG. 4 is a process flow diagram 400 for recovering from a memory modulefailure under some embodiments of the present disclosure. This processwill be described with reference to elements of FIGS. 1 and 2 forclarity.

The process may start at block 402 in which a memory module failure maybe detected by host machine 102. In some embodiments, the memory modulefailure may be detected through the use of machine check architecture(MCA) recovery mechanism of host machine 102. One of ordinary skill willappreciate that any method of detecting the memory module failure couldbe utilized without departing from the scope of the disclosure.

In block 404 VMM 104 may be notified of the memory module failure. Thismay be done through the host OS, memory controller 206, or firmware ofhost machine 102, depending upon the configuration of the host machine102. In some embodiments, this notification may include identificationof the faded memory module. In other embodiments, this notification mayinclude an address range of the failed memory module.

At block 406 VMM 104 may identify virtual machine allocations thatinclude the failed memory module. This may be done with reference to therecorded memory allocation details described in the discussion of FIG. 3above. To accomplish this, VMM 104 may cross-reference the recordedmemory allocations utilizing the information included with the memorymodule failure notification to determine which virtual machine ormachines have been allocated to the failed memory module.

At block 408, VMM 104 may determine whether any virtual machine ormachines are affected by the memory module failure. If no virtualmachines are affected then the process may end. If one or more virtualmachines are affected by the memory module failure then the process maycontinue onto block 410.

At block 410 VMM 104 may stop the identified virtual machine, machines,without stopping the unaffected virtual machines. At block 412 VMM 104may reallocate other memory resources to the identified virtual machineor machines, and restart the affected virtual machine or machines withthe new memory allocations. The reallocation may be accomplishedutilizing the same process described in reference to FIG. 3 blocks312-318. Prior to the restart of the affected virtual machines, to theextent possible, VMM 104 may recover and migrate the recovered data fromthe prior allocated memory modules to the newly allocated memorymodules.

FIG. 5 is a diagram depicting the recovery process according to someembodiments of the present disclosure. 502 is a depiction of the memoryallocation of virtual machines VM1-VM5 of FIG. 1 at a first instance intime according to some embodiments of the present disclosure. In thisembodiment, the host OS or a firmware loader has loaded and initializedVMM 104 in memory module 204 i, utilizing the minimum number of memorymodules to satisfy the memory requirements of VMM 104. In addition, VMM104 has performed a selective memory allocation in which virtualmachines VM1-VM5 are allocated to the minimum number of memory modulesto satisfy the respective memory requirements of virtual machinesVM1-VM5. As depicted memory module 204 a has been allocated to VM1,memory module 204 b has been allocated to both VM2 and VM3, memorymodule 204 c has been allocated to VM4 and 204 d has been allocated toVM5. Memory modules 204 e-204 i have yet to be allocated. Thisallocation may be arrived at through the allocation process described inreference to FIG. 3.

504 depicts a memory module failure at a second instance of time, laterthan the first instance of time. In this scenario memory module 204 chas experienced a failure. Host machine 102 would detect this error andeither notify VMM 104 through a mechanism of the hardware or notify thehost OS which would in turn notify VMM 104 of the memory module failure,depending on the configuration of host machine 102.

506 depicts the response to the memory module failure after receipt ofthe failure notification. In response to the notification of memorymodule failure, VMM 104 would stop VM4. The memory module may also bemarked as unusable by VMM 104, memory controller 206, or othermechanisms of host machine 102. In some embodiments, memory controller206 may be adapted to mark the memory module as unusable; however, thisdisclosure is not to be so limited. Any mechanism for marking the memorymodule as unusable could be used without departing from the scope ofthis disclosure.

508 depicts the reactivation of VM4 by VMM 104. In this scenario, VMM104 has selectively allocated memory module 204 e for VM4. Thisselective memory allocation is described in reference to FIGS. 3 and 4.As described earlier, to the extent possible, VMM 104 may recover andmigrate the recovered data from memory module 204 c to 204 e.

Embodiments of the disclosure can take the form of an entirely hardwareembodiment, an entirely software embodiment or an embodiment containingboth hardware and software elements. In a preferred embodiment, thedisclosure is implemented in software, which includes but is not limitedto firmware, resident software, microcode, and the like. Furthermore,the disclosure can take the form of a computer program productaccessible from a computer-usable or computer-readable medium providingprogram code for use by or in connection with a computer or anyinstruction execution system.

For the purposes of this description, a computer-usable or computerreadable medium can be any apparatus that can contain, store,communicate, propagate, or transport the program for use by or inconnection with the instruction execution system, apparatus, or device.The medium can be an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system (or apparatus or device) or apropagation medium. Examples of a computer-readable medium include asemiconductor or solid state memory, magnetic tape, a removable computerdiskette, a random access memory (RAM), a read-only memory (ROM), arigid magnetic disk and an optical disk. Current examples of opticaldisks include compact disk-read only memory (CD-ROM), compactdisk-read/write (CD-RW) and DVD.

Thus, what has been described herein includes apparatus, at least onemachine readable storage medium and methods that may provide a memorycontroller configured to provide a layout of memory modules. Inembodiments, an apparatus may include a processor, a number of memorymodules, and a memory controller coupled with the processor and thememory modules, and configured to provide a layout of the memorymodules. The apparatus may further include a virtual machine manager(VMM) configured to be operated by the processor to manage execution ofvirtual machines by the processor including selective avocation of thememory modules to the virtual machines using the layout of the memorymodules provided to the VMM by the memory controller.

In embodiments, the VMM may be configured to employ a memory allocationutilizing the minimum number of memory modules to meet the memoryrequirement. In embodiments, the VMM may be configured to employ amemory allocation utilizing the smallest number of memory modules tomeet the memory requirement.

In embodiments the VMM may be configured to receive the layout of thememory modules and a memory requirement from a virtual machine. The VMMmay determine the minimum number of memory modules to be allocated, inwhole or in part, to meet the memory requirement of the virtual machine,and allocate the minimum number of memory modules to the virtualmachine.

In embodiments, the memory controller may be configured to alert the VMMin the event of a failure of a memory module. The VMM may be configuredto identify, in response to an alert of a memory module failure, avirtual machine with a memory allocation that includes the faded memorymodule. The VMM may stop the virtual machines with a memory allocationthat includes the failed memory module. The VMM may re-allocate, to thevirtual machine, a new memory allocation that does not include thefailed memory module. The VMM may restart the virtual machine with thenew memory allocation.

In embodiments, the memory controller may be configured with machinecheck architecture (MCA) recovery enabled hardware to detect failures ofmemory module. In embodiments, the VMM may be configured to allocate amemory module to at most one virtual machine. In embodiments the memorycontroller may be configured to allocate the smallest number of memorymodules for the VMM to reside on.

In embodiments, the at least one machine-readable storage medium maycomprise instructions configured, in response to execution by aprocessor of a computing device, to provide the computing device with avirtual machine manager (VMM). In embodiments, the VMM may be equippedto manage execution of virtual machines by the processor. In furtherembodiments, the VMM may be equipped to include selective allocation ofmemory modules, of the computing device, to the virtual machines. TheVMM may be equipped to use a layout of the memory modules provided by amemory controller of the computing device. In embodiments, the VMM maybe configured to employ a memory allocation that utilizes the leastnumber of memory modules to meet the memory requirement.

In embodiments, the VMM may be configured to receive the layout of thememory modules. The VMM may be configured to receive a memoryrequirement from a virtual machine. The VMM may determine a minimumnumber of the memory modules to be allocated, in whole or in part, tomeet the memory requirement of the virtual machine, and allocate theminimum number of memory modules to the virtual machine.

In embodiments, the VMM may be configured to receive, from the memorycontroller, an alert of a memory module failure. The VMM may beconfigured to identify, in response to an alert of a memory modulefailure, a virtual machine with a memory allocation that includes thefailed memory module. The VMM may stop the virtual machine with a memoryavocation that includes the failed memory module. The VMM mayre-allocate to the virtual machine a new memory avocation that does notinclude the failed memory module. The VMM may restart the virtualmachine with the new memory allocation.

In embodiments, the at least one machine-readable storage medium mayfurther comprise instructions which, when executed by a processor of thecomputing device, cause the computing device to allocate the smallestnumber of memory modules for the VMM to reside on.

In embodiments the method may include receiving, by a virtual machinemanager (VMM) operating on a host machine, a layout of memory modules ofthe host machine. In embodiments the method may include receiving, bythe VMM, a memory requirement of a virtual machine managed by the VMM.In embodiments the method may include selectively allocating, by theVMM, the memory modules to meet the memory requirement of the virtualmachine, using the layout of the memory modules.

In embodiments, the method may include determining, by the VMM, aminimum number of memory modules for the virtual machine. The method mayinclude allocating, by the VMM, the minimum number of memory modules forthe virtual machine.

In embodiments, the method may include alerting the VMM of a memorymodule failure. The method may further include identifying, in responseto an alert of a failed memory module, a virtual machine with a memoryallocation that includes the failed memory module. The method mayinclude stopping the virtual machine with a memory allocation thatincludes the failed memory module. The method may include re-allocating,to the virtual machine, a new memory allocation that does not includethe failed memory module; and restarting the virtual machine with thenew memory allocation. In embodiments, the method may include utilizingmachine check architecture (MCA) recovery enabled hardware in detectinga memory module failure.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a wide variety of alternate and/or equivalent implementations maybe substituted for the specific embodiments shown and described, withoutdeparting from the scope of the embodiments of the disclosure. Thisapplication is intended to cover any adaptations or variations of theembodiments discussed herein. Therefore, it is manifestly intended thatthe embodiments of the disclosure be limited only by the claims and theequivalents thereof.

What is claimed is:
 1. An apparatus, comprising: a processor; aplurality of memory modules; a memory controller coupled with theprocessor and the memory modules to provide a layout of the memorymodules; and a virtual machine manager (VMM) to be operated by theprocessor to manage execution of virtual machines by the processorincluding selective allocation of the memory modules to the virtualmachines using the layout of the memory modules provided to the VMM bythe memory controller.
 2. The apparatus of claim 1, wherein the VMM isto employ a memory allocation that utilizes the minimum number memorymodules to meet the memory requirement.
 3. The apparatus of claim 1,wherein the VMM is to employ a memory allocation that utilizes thesmallest number memory modules to meet the memory requirement.
 4. Theapparatus of claim 1, wherein the VMM is to: receive the layout of thememory modules; receive a memory requirement from a virtual machine;determine a minimum number of the memory modules to be allocated, inwhole or in part, to meet the memory requirement of the virtual machine;and allocate the minimum number of memory modules to the virtualmachine.
 5. The apparatus of claim 1, wherein the memory controller isfurther to alert the VMM of a failure of a memory module in the memorymodules.
 6. The apparatus of claim 5, wherein the VMM is further to:identify, in response to the alert of the failed memory module, avirtual machine with a memory allocation that includes the failed memorymodule; stop the virtual machine with a memory allocation that includesthe failed memory module; re-allocate to the virtual machine a newmemory allocation that does not include the failed memory module; andrestart the virtual machine with the new memory allocation.
 7. Theapparatus of claim 5 wherein the memory controller includes machinecheck architecture (MCA) recovery enabled hardware to detect failures ofthe memory module.
 8. The apparatus of claim 1, wherein the VMM is toallocate a memory module to at most one virtual machine.
 9. Theapparatus of claim 1, wherein the memory controller is further toallocate the smallest number of memory modules for the VMM to reside on.10. At least one non-transitory machine-readable storage mediumcomprising instructions which, in response to execution by a processorof a computing device, provide the computing device with a virtualmachine manager (VMM) equipped to manage execution of virtual machinesby the processor, including selective allocation of memory modules ofthe computing device to the virtual machines using a layout of thememory modules provided by a memory controller of the computing device.11. The at least one machine-readable storage medium of claim 10,wherein the VMM is to employ a memory allocation that utilizes the leastnumber of memory modules to meet the memory requirement.
 12. The atleast one machine-readable storage medium of claim 10, wherein the VMMis to: receive the layout of the memory modules; receive a memoryrequirement from a virtual machine; determine a minimum number of thememory modules to be allocated, in whole or in part, to meet the memoryrequirement of the virtual machine; and allocate the minimum number ofmemory modules to the virtual machine.
 13. The at least onemachine-readable storage medium of claim 10, wherein the VMM is toreceive, from the memory controller, an alert of a memory modulefailure.
 14. The at least one machine-readable storage medium of claim10, wherein the VMM is to: identify, in response to an alert of a memorymodule failure, a virtual machine with a memory allocation that includesthe failed memory module; stop the virtual machine with a memoryallocation that includes the failed memory module; re-allocate to thevirtual machine a new memory allocation that does not include the failedmemory module; and restart the virtual machine with the new memoryallocation.
 15. The at least one machine-readable storage medium ofclaim 10, further comprising instructions which when executed by aprocessor of the computing device cause the computing device to allocatethe smallest number of memory modules for the VMM to reside on.
 16. Amethod comprising: receiving, by a virtual machine manager (VMM)operating on a host machine, a layout of memory modules of the hostmachine; receiving, by the VMM, a memory requirement of a virtualmachine managed by the VMM; selectively allocating, by the VMM, thememory modules to meet the memory requirement of the virtual machine,using the layout of the memory modules.
 17. The method of claim 16,further comprising: determining, by the VMM, a minimum number of memorymodules for the virtual machine; and allocating, by the VMM, the minimumnumber of memory modules for the virtual machine.
 18. The method ofclaim 16, further comprising alerting the VMM of a memory modulefailure.
 19. The method of claim 18, further comprising: identifying, inresponse to an alert of a failed memory module, a virtual machine with amemory allocation that includes the failed memory module; stopping thevirtual machine with a memory allocation that includes the failed memorymodule; re-allocating, to the virtual machine, a new memory allocationthat does not include the failed memory module; and restarting thevirtual machine with the new memory allocation.
 20. The method of claim18, further comprising utilizing machine check architecture (MCA)recovery enabled hardware in detecting a memory module failure.